Extreme Cosmic Explosions Supercharged by Magnetism

An artist's illustration of how theoretical models link the presence of strong, stable polarized light in a gamma-ray burst's jet with a large-scale magnetic field (a blue spiral) originating from the newly formed black hole.

NASA's Goddard Space Flight Center/S. Wiessinger

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TheMostMind-BlowingSpaceSpirals:Photos

View Caption+#1: A Dying Star's Radio Spiral

Oct. 19, 2012 -- Meet R Sculptoris, a dying star that is shedding its outer layers of gas, generating a beautiful spiral of radio emissions. This amazing sight was captured by the newly commissioned Atacama Large Millimeter Array (ALMA) in the Chilean desert. Although rare, this kind of space spiral isn't unprecedented. In fact, there have been several spirals seen in recent years that have excited, spooked, but, above all, awed onlookers -- here are a few of the most memorable.

Credit: ALMA (ESO/NAOJ/NRAO)

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Hubble's Ghost Spiral
In 2010, the Hubble Space Telescope imaged a ghostly pinwheel spiral surrounding a binary star system called LL Pegasi.
This bizarre cosmic phenomenon is caused by one of the stars dying, venting huge amounts of gas and dust into space. As the stars orbit one another every 800 years, the material expands into space like water being sprayed from a spinning garden sprinkler.

Credit: NASA/ESA/HST

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The Failed Missile Spiral
Probably the most striking example in recent years is that of the mysterious expanding shape that appeared over northern Norway on Dec. 9, 2009.
Reflecting the early morning Arctic light, this vast spinning cloud expanded above the horizon, spraying a white spiral and blue tail.
Conspiracy theories swarmed as soon as photographs and videos hit the media. Was it a portal to another dimension? Did a black hole just appear in our atmosphere? Was the restarted Large Hadron Collider responsible?
As it turned out, the spiral was caused by a Russian missile after a failed test launch. The rocket, designed to carry nuclear warheads, spun out of control spewing fuel into the upper atmosphere, creating this beautiful spiral display.

Credit: Jan Petter Jørgensen via Vaeret

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The Death Star Spiral
What a kerfuffle WR 104 caused in 2008.
The Wolf-Rayet star first gained attention when astronomers admired its spectacular spiral created by stellar winds colliding with the winds of its binary partner. But then we realized something. The Wolf-Rayet was dying, violently. And its violent death meant the massive star could collapse and generate one of the most powerful explosions in the cosmos: a gamma ray burst (or GRB).
WR 104 is only 8,000 light-years from Earth, and the fact that we can see its full spiral means that we are looking down the barrel of this potentially damaging GRB.
Naturally, many people were concerned that we could become GRB toast and in the eyes of the media, WR 104 was dubbed the "Death Star."
Fortunately in 2009, Discovery News spoke with Wolf-Rayet star expert Grant Hill, of the Keck Observatory in Hawaii, who has other ideas about the deadly potential of WR 104.

Credit: Keck Observatory

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The UFO Spiral
UFO reports are often vague and include shaky video footage of a fuzzy light in the sky.
However, when the Australian press announced the arrival of a bizarre spiraling light over the Gold Coast in June 2010, many eyewitnesses captured high quality video and photographs of the event.
At the time, this "UFO" stayed true to its description; it was certainly an unidentified flying object.
But it didn't stay unidentified for long; the sightings coincided with the maiden flight of SpaceX's Falcon 9 rocket. The spiraling effect was caused by a slight engineering fault causing the rocket to spin slowly, venting exhaust in a partial spiral.

Credit: Haribolman (YouTube screenshot)

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The Recurrent Nova Spiral
We've all heard of supernovae, but what are "recurrent novae"?
In the case of the binary star system RS Ophiuchi, a small but dense white dwarf star orbits with a large, puffy red giant that is shedding huge quantities of matter. This matter is blasted into space in the form of a strong stellar wind, forming a spiral.
Interestingly, in this star system, the white dwarf captures some of the gas from its companion star, gradually accumulating it.
Once the gas reaches a critical mass and temperature, a massive explosion occurs, wiping out the expanding spiral. The process then repeats every 20 years or so.
For more about this special star system and how novae can help to enrich the interstellar medium with heavy elements, read the Discovery News IM interview with nova expert Richard Barry of NASA Goddard Space Flight Center.

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DESY

The new research tracked polarized light from cosmic explosions, known as gamma-ray bursts, and offered an unprecedented glimpse into how intense magnetic fields shape the evolution of the outbursts.

"Gamma-ray bursts are the most extreme particle accelerators in the universe," said Carole Mundell, a professor of extragalactic astronomy at Liverpool John Moores University, who led the new study. "They're objects of all kinds of extremes: extreme speeds, extreme gravity, extreme magnetic fields. So they're the ultimate laboratory for testing or laws of physics." [10 Strangest Things in Space]

Gamma-ray bursts are believed to form at the end of a massive star's life, just as the body of the star collapses in on itself, creating a black hole. As this happens, the matter surrounding the black hole may release two jets of gamma-rays and highly energetic particles, in opposite directions away from the black hole. A single gamma-ray burst may radiate more energy in a few minutes than the star radiated in its entire lifetime.

Mysterious Origins of Cosmic Explosions

Scientists still don't understand how the particles surrounding a black hole can generate the intense bursts of light and particles seen in gamma-ray bursts.

One theory suggests that an organized magnetic field will accelerate particles on an invisible track around the black hole, causing them to radiate light (what's known as synchrotron radiation). As the black hole rapidly contracts, so do the particles and the magnetic field, causing the particles to accelerate even faster. The theory suggests that it is this rapid bump in acceleration, combined with energy stored in the particles themselves, that creates two massive jets of gamma-rays and particles.

If the energy in a gamma-ray burst was at least partly due to synchrotron radiation, then scientists could expect to see an imprint of that magnetic field in the light produced by this violent event.

New Telescope Tool's Magnetic Find

Mundell and her colleagues designed an instrument named RINGO2 to measure the polarization of optical light that is produced as a byproduct of a gamma-ray burst. RINGO2 observed gamma-ray bursts for two years on the Liverpool optical telescope.

On March 8, 2012, NASA's Swift satellite — which tracks gamma-ray bursts — alerted the Liverpool telescope to a cosmic explosion dubbed GRB 120308A. The subsequent study, which was detailed in the Dec. 5 edition of the journal Nature, found that optical light emitted early on by GRB 120308A was 28 percent polarized, and decreased to 10 percent polarization over time.

"If you take optical light and you scatter it from dust, as it comes through our Milky Way galaxy, you might observe a few percent polarization," Mundell said. "Really the only way to produce this high degree of polarization is to have large-scale ordered magnetic fields that are producing the synchrotron radiation with the electrons spiraling around the magnetic field."

Mundell said the reduction in the polarization of the light over time demonstrates that the light is polarized upon its creation near the black hole, and loses its polarization as it travels through space. For this reason, RINGO2 must observe the optical light almost immediately after the start of the gamma-ray burst, in order to observe the polarity.

More observations of polarized light in future gamma-ray bursts are needed to confirm the findings, the researchers said. RINGO2 operated on the Livermore telescope for two years and collected data on multiple gamma-ray bursts.

"We're in the process of working on a sample paper about those other gamma-ray bursts," Mundell said. "Obviously, we want to look at more of them and really prove that this is a universal case and not just a special object. [GRB 120308A] wasn't special in any other way, and that's one good reason to suggest that it was typical."